Roasting-furnace.



F. LAIST. ROASTING FURNAGE. AEPLIUATION FILED 00T. 15, 191s.

Patented Oct. '20, 1914.

3 SHEETS-SHEET l.

F. LAIST.

ROASTING FURNACE. APPLICATION FILED 0017.15, 1913.

1,1 14,371 Patented Got. 20, 1914.

3 SHBETSSHEBT 2.

JIET- F. LAIST.

ROASTING PURNAGE.

APPLICATION YILBD 001.15, 1913.

1,1 14,371 Patented oct. 20, 1914.

3 SHEETS-SHEET 3.

' on the line `3 UNITED STATES PATENT OFFICE.

FREDERICK JA'IST, OF ANACONDA, MONTANA.

ROASTING- EURNACE.

Specification of Letters Patent.

Patented oct. 2o, 1914.

Application flied october 15, 1913. serial No. 795,321.

ments in roasting furnaces; and it consistsA in the novel details of construction more fully set forth in the specification and pointed out in the claims.

In the drawings, Figure l is a combined elevation and middle vertical section of the furnace, the section being taken through one of the fire-boxes; Fig. 2 is an enlarged vertical sectio-n of a portion of the furnace taken on the line 2--2 of Fig. 3, parts being in elevation; Fig. 3 is a horizontalsection 3 of Fig. 1, parts being broken away; Fig. 4 is a detail in horizontal plan of a cluster of tiles foi-mine the Hoor of the second hearth, or the roof of the combustion chamber; and Fig. is a vertical sectional view of Fig. 4 on the line-5 5 of said Fig. 4.

The, present invention is an improvement on the construction of roasting furnace covered by my U. S. Patent Num-ber 1,070,490, dated August 19, 1013; and while contemplating the several objects and possessing the various advantages as the patented structure, the improved furnace herein is characterized bythe presence of a muflle, or combustion chamber, interposed between the second and third top hearths into the lower one of which the products from thegmuftle directly pass. This inutiley is supported over the dome of the third hearth, special provision being made in said dome to permit the gases from the fire-box after-they have traversed the combustion-chamher to circulate downward over thc floor of the third hearth and thence up through the drop-holes connecting the lsecond and third hearths, and finally up through the stack. By this arrangement there is promoted a gradual and less intense heating. of the ore (undergoingT the oxidizing roast) and at'the same time a more perfect combustion ofthe smoke and gases from the fire-boxes, results The advantages of the improvement will be fully .apparent from a. detailed descrip` present invention.

tion of the invention, which isas followsz Referring to the dra wings, F represents the furnace, and a, Z), c, e, f, g, the several superimposed floors or hearths in which the material is treated (the, present being a .seven-hearth multiple-hearth furnace ofthe McDougal type) the material dropping from the upper hearth successively through the several hearths until it reaches the discharge screw S by which it is conducted to any suitable oint for further treatment, the hearths being provided with central and marginal openings or drop-holes o, 0', re-

spectively for the passage of the material.

Passing centrally through the hearths is the rotatable hollow rabble-shaft 1 from which radiate the series of hollow rabble or stirrer arms 2 extending into the several hearths and carrying rakes 3, by whiclrthe material is successively fed from one hearth to the hearth immediately beneath it, the shaft and arms being provided with air-circulating pipes l), P, as 'well understood in lthe art. The drive for the rabble mechanism While here illustrated, is not described because well. understoodand forming n part of the Neither is any description entered into herein, of the ore-feed mechanism H. a conventional illustration thereof sufticing for the present purpose.

Like the structure of the patent vreferred to, the present is a combination roasting and chloridizing furnace, the ore being subby direct fire in hearths (L, 1),0, and to a .-hloridizing roast in hearths d, e, f, g. In

the present embodiment of my invention Mhowever, a change has taken place in the second and thlrd direct-fired hearths b, c,

said change being substantially as follo\\s:-I)isposed above the roof or dome of the bottom hearth c of the series of directred or oxidizing (As'ulfating) hearths, is a combustion chamber C into which the Haine and hot gases from the fire-boxes B immediately discharge, the dome of the hearth c constituting the Hoor of'said chamber C, the roof of the combustion chamber being flat and horizontal and composed of tiles 4 (about two or three inches thick) laid so as to overlap one anotl1er,and supported by hollow piers of {ire-brick 5, resting on the floor of the chamber, one pier supporting four tiles as .shown (a pier being placed at the meeting or point of convergence of four tiles as best shown in Fig. 4). The roof of hearth c (or what is the same thing, the

floor of the chamber C) is provided withv series of'y openings O and O, O', O, arranged along lines radial from the axis of the furnace, the series O, O', O, being disposed at right angles to the generaldirection` of projection of the gases from the fire boxes B, B, into said combustion chamber, and progressively enlarging in area as their distance from the axis of the furnace increases, said progressive areal enlargement being conformable to the progressive expansion of the gases from the axis of the furnace outwardly (Figs. 2, 3)'. Between the third and fourth hearths c, d (always starting from the top of the furnace) are discharge hoppers 6 for the roasted calcines, which deliver the material from the last oxidizing hearth c to the first chloridizing hearth d, the said hoppers being on the order of the hoppers 23 in my patent aforesaid, and hence requiring no special description in the present connection. In the present furnace however, the peripheral drop holes o are formed partly in the outer furnace-wall and partly in the floor between two superimposed hearths, the holes being spanned by arched blocks 7; and in the second hearth (b) the floor of which issupported by the roof of the third hearth, the block 7 supports an arched block 7 likewise spanning the drop-hole, the ends ofy the block abutting against the bevel ends of special brick 8 set in the wall on either side of the drop-hole (Fig. 3) the top of the upper brick 8 being raised above the upper surface of the block (7') to come even with the upper surface of the tiles 4 which said block 7 helps to support, theA drop-holes of course, having no communication with the chamber C. In all instances the' recess 1' formed in the wall of the furnace (to bring the drop-hole partly in the wall and partly in the floor separating two contiguous hearths) extends partly above and partly below the floor of a hearth, making it easy for the material to discharge at these points. Obviously the drop hole o between hearths b and c will be elongated vertically, traversing as'it does, the blocks 7, 7, as againsta block 7 in the other hearths. The construction of the drop-hole o is not however claimed herein.

As stated above, the present is a combined oxidizing and chloridizingfurnace on the order of the o ne covered by my patent aforesaid, the hearth d which forms the top hearth of the series of chloridizing hearths receiving the roasted calcines from the hearth c.' In the present furnace he salt which forms acomplement of the charge for the chloridizing hearths is introduced into the hearth d from a salt-hopper N the discharge from which is controlled by a rotary feeder-valve V in conjunction with which cotiperates an injector pipe 9 which projects or sprays the salt into this hearth.

.lhis feature however, is merely incidentally referred to, and not claimed, because not forming a part of the main feature to which the present improvement is directed. The openings O, O, O, are preferably formed in special tiles or blocks 10 set in the cement Hoor of the combustion chamber as shown. Like in my patented construction, there is maintained in the present furnace a pressure -differential between thev chloridizing hearths d, c, f, g, and the roasting or sulfating hearths a, b, c., In the improved furnace however, the gases are drafted downward through (and out of) the severalchloridizing hearths instead of upward, suitable suction' mains M having branches m, m', leading to the hearths f and g respectively, serving to draft the fumes from said hearths, the fourth hearth d (the first of the series of chloridizing hearths) being provided with an air intake opening A as shown. In this way the pressure differential between the two sets of hearths is maintained, the same as in my patented construction, the draft of the fumes being downward instead of upward. The mains M may be connected to any suitable single exhauster (not shown) disposed where most convenient and as fully understood by the skilled mechanic.

The present furnace is air-cooled, that is to say, the rabble mechanism is cooled by a current of air entering the pipe P at the top, the air circulating through the pipes P, P, and hollow rabble arms 2 and shaft l, whence it discharges through nozzles n, n, at the top of the shaft into a draft elbow R coupled to the branch R of the exhauster E, whence it may be discharged into the .stack (not shown). The method of cooling however, is not claimed herein, being well understood in the art.

In a furnace' of the character here described, the interposition of the mufe, or combustion chamber C betweenthe second and third hearths (b, c) is important, as practical experience has shown. It is to be remembered that (and as fully explained in my patent aforesaid) an overheating of the charge in the sulfa'ting hearths is liable to produce insoluble ferrite copper (where copper ores are treated), the temperature inthe hearth into which the gases from the fire-boxes lB immediately discharge reaching as high as 1280 degrees Fahr.; and in ther patent aforesaid the deleterious effects of this high temperature was attempted toj be overcome by rabbling and advancingthe ore from the periphery toward the center of the hearth. rI`his inward (radial) advance of the material is maintained in the present improvement (in the hearth o), but the material no longer has to contend with the high temperature 4alluded to, the mulle C having the effect of tempering the excessive heat of the fire gases before such gases reach the hearth c. By following the feathered arrows in Fig. 1 (the plain arrows representing the course pursued by the ore or charge) it will be noticed that the flame, gases and lcombustion products from the fire-boxes B passV through the peripheral walls of the furnace into and toward the center of the combustion chamber C, being more or less broken and deflected by the hollow piers or posts 5, the gases spreading on either side of/the axis of the furnace and then descending and discharging through the openings O, O, O', O, formed in the floor of the chamber (the row of openings 0, O', O, being disposed on a radial line substantially a't right angles to the general direction of projection of the gases from the fire-boxes into the chamber) into the hearth c, the gases circulating outwardly in said hearth toward the peripheral drop-holes 0 between the hearths c and b, escaping through said holes (past the descending ore) into the hearth b, whence they pass through the central drop-hole o between hearths a and b, into the hearth a, and out from said hearth through the pipes R, R, into the discharge main R', and thence to the stack (not shown). The traverse of the gases from the fire-boxes, directly throu h the combustion chamber or muflie C, has t e eect of so tempering the heat of said gases, and so insuring their complete combustion, that by the time they come in contact with the ore charge in the hearth c, the charge is no longer in danger of overheating. In other words, the combustion chamber or mulie C promotes a gradual and less intense heating of the ore assing through the furnace, and nsecures or the smoke and gases from the fire-boxes a more perfect combustion. By the time the ore reaches the hearth d, it is in excellent condition for chloridizing. y

Features illustrated but not alluded to, and forming well known accessories to a i roasting furnace are not here described,

formingno part of the present invention. So far as the present invention is concerned,

the fseries of superimposed hearths may be any number, the invention not being restricted to any specific number of hearths, either for the oxidizing set or the clilofidizing set. It is to be further understood that the mufiie or combustion chamber C or its equivalent may be used in conjunction with any set of oxidizing or roasting hearths, be the latter associated with a set `of chloridizing hearths or not, or be lthey' associated with such latter set in the same structure `or not. Y

Having described my invention, what I v claim is l. In combination with a furnace having a series of superimposed intercommunicating hearths, means for subjecting the charge in the hearths to direct fire, a chamber iiiterposed between two contiguous hearths and provided with radially disposed openings in the `floor thereof for establishing communication with the lower hearth, the latter discharging the gases into the hearth above the chamber through the intercommunicat-ing openings between the hearths.

2. In combination with a furnace having superimposed intercommunicating hearths, means for subjecting the charge in the hearths to direct fire, a chamber interposed between two conti uous hearths for immediately receiving t e gases from the firing means, the bottom of the chamber being provided with radially disposed openings centered about the axis of the furnace for establishing communication between the chamber and lower hearth, suitable drop openings being disposed between the peripheral or outer portions of the h rths for conducting the gases from the hearth below the chamber to the hearth above said chamber.

3Q In combination with a furnace having superimposed intercoinmunicating hearths, a combustion chamber interposed between two contiguous hearths and communicating with the lower hearth at points disposed radially about the axis of the furnace, means for introducing..` burning combustion products into said chamber from points along the periphery of the furnace whereby said products circulate downward from said combustion chamber into the lower hearth, and upward through the intercommunicating moans between the hearths.

4. In combination with a furnace having superimposed intercommunicating hearths, an annular combustion chamber interposed between two contiguous hearths, the roof of lthe lcwer hearth forming the floor of said combustion chamber, a roof for `the combustion chamber, suitable posts or props interposed between the floor and roofl of the combustion chamber for supporting said roof, means for introducing heated products of combustion through the peripheral wall of the furnace into said combustion chaillber, means for conducting said products from the combustion chamber into the lower hearth at a multiple of points disposed about the axis of the furnace, means for conduct ing the gases from the lower to the upper hearth at points adjacent the periphery of the furnace, said l'ast mentioned conducting means haying no communication with the combustion chamber, whereby a circulation of the products is established from the periphery o f the furnace toward the coinbustion chamber and the center of the lower hearth, and from said center toward the peripheries of the respective hearths.

5. In combination with a furnace having superimposed hearths communicating with one another at points adjacent the periphery of the furnace, a combustion chamber interposed between the hearths, lire-boxes operating to discharge into the combustion chamber at poirfts diametricaliy opposite Ione another along the periphery of the furnace, the fioor of the combustion chamber being provided withopenings disposed along lines radiating from the axis of the furnace at subetantialiy righty angles to the direction o1 projection of the fire gases into the combustion chamber for establishing communication between the combustion chamber and lower hearth, whereby the com 'bustion products from the fire-boxes circulate toward the combustion chamber, thence downward into the lower hearth, the'n outward and upward into the upper hearth.

'6. In a furnace of the character described, a combustion chamber having discharge cpenings in the fioor thereof disposed on lines radiating from the axis of the furnace, the areas of the respective openings increasing with their distance from said axis.

In testimony whereof I affix my signature, in presence of two Witnesses.

FREDERICK LAST. 1Witnesses ALBERT E. iVIGGIN, W. H. SHEERIN. 

